1. Field of the Invention
The present invention relates to a printing method and a printing system for printing an image on a printing medium under control by a control unit.
2. Description of the Related Art
In general, in a printer employing a printing head ejecting an ink from ink passages forming a plurality of nozzles, it is possible to cause density fleck in a printed image due to adverse effect of fine fluctuation of shapes of the ink passage forming the nozzles or to variation of ejection amount of the ink as printing material. One of the correction methods to make such density fleck not perceptible is called as head shading (HS).
FIG. 8 is a general block diagram showing a system actually performing head shading. Hereinafter, at first, the conventional head shading technology in the case where three systems of reading, image processing and printing are constructed in a single apparatus.
In FIG. 8, an original exposure system 801 is a portion performing reading of an original, forms a portion of reading a result of printing necessary for performing head shading. An image processing portion 802 serves as a portion performing arithmetic operation and the like with respect to the image read by the original exposure system 801. The arithmetic operation performed in the image processing portion 802 includes color processing, binarizing process, head shaping and so on. An image forming portion 803 is a portion for printing an image read by the original exposure system 801 and processed by the image processing portion 802. The image forming portion 803 includes printing heads 804 to 807 for printing the images. In the shown example, 804 denotes a head for ejecting a black ink, 805 denotes a head for ejecting a cyan ink, 806 denotes a head for ejecting a magenta ink and 807 denotes a head for ejecting a yellow ink.
In the printer constructed as set forth above, in order to check output characteristics of respective of the printing heads 804 to 807 in the image forming portion 803, printing of the predetermined test pattern is performed so that an image of the predetermined density is formed by respective of the printing heads 804 to 807. Then, the resultant print is read by the original exposure system 801. A read data read by the original exposure system 801 is used for forming a HS data 808 in the image processing portion 802. The HS data is data for correcting output density of ink per ink passage forming a plurality of nozzles in respective of the printing heads 804 to 807. The HS data 808 is used as a correction data for the image data input from the original exposure system 801 so as to make the density fleck not perceptible. As a result, an image avoided the density fleck is printed by the image forming portion 803.
In the printer constructed as set forth above, the original exposure system 801, the image processing portion 802 and the image forming portion 803 will never been separated individually. Therefore, a discrepancy such as that explained later, will never be caused between the characteristics of the printing heads 804 to 807 in the image forming portion 803 and the HS data 808.
On the other hand, in a printing system, in which a reader device 3, a computer terminal device 2 which can perform image processing and transmission, and a printer 1 are mutually independent, and connected through connection cable 5, as shown in FIG. 1, it is possible that the printer 1 is replaced with other printer.
In the system construction as illustrated in FIG. 1, when the printer 1 connected to the computer terminal device 2 is replaced, a discrepancy is inherently arisen between the characteristics of the printer and the HS data managed by the computer terminal device 2 to make it impossible to perform appropriate data correction. Therefore, in the prior art, head shading cannot be performed in the system shown in FIG. 1.
On the other hand, in the system construction set forth above, if condition of formation of the density fleck is varied due to secular change, it is possible that the HS data cannot be adapted to the secular change of the head to make it difficult to effect appropriate data correction. Particularly, where the printer is changed, appropriate data correction cannot be performed unless the HS data corresponding to the printer and the timing where the HS data is generated, are properly managed.